Sensory substitution and the design of an artificial ear.

This paper is concerned with attempts at sensory substitution and in particular with devices that have been designed to substitute for hearing by using the skin as an alternative channel of communication. A review of the literature suggests that the failure or limitations of tactile substitution systems are due, not to the inadequacy of the skin's perceptual processing capacity, but to inappropriate displays, ineffective training methods, or insensitive testing techniques. Specifically, displays have been artificial in that they have typically failed to preserve the information relevant to the modality for which they are supposed to substitute. Furthermore, certain false assumptions and misconceptions have been manifest in testing techniques which have not taken into account the way in which perceptual processes normally develop and operate. The result has been that some important evidence has been ignored or has gone unnoticed and that some promising devices have been prematurely abandoned. In the final section of the review, some suggestions are made concerning the design, application, and evaluation of an artificial ear.